Tents are set up at the forest in Bac Ai District to protect the trees.

According to the Ninh Thuan Provincial Department of Agriculture and Rural Development, over 200 trees with diameters of between 10-20 cm had shown signs of being poisoned with herbicides, including seven that were already dead. Herbicides were found inside holes drilled on the trees. Lots of herbicide bottles were found around the area.

"This is the first time such a case has occurred in this area," the department said. "The forest management board is trying to save the trees by pouring water into the hole to wash out the herbicides."

Pine forests in the central highlands province of Lam Dong have also been destroyed in similar ways by people who wanted to take the land for farming.